event-sourcing-poc

Event Sourcing POC

This project aims to explain how to use event-sourcing to synchronize data between 3 services.

academic-service: the service that owns the data and publish events in event-sourcing and event-carried-state-tranfer ways
avalia-service: the service that uses event-sourcing to syncronize application
classroom-service: the service that uses event-carried-state-transfer to syncronize application

Infrastructure Services

The project has an "infra" directory containing a docker-compose.yml file.

This docker-compose will start Kafka (with Zookeper) and MySQL8 server.

To start servers, you should use:

docker-compose up

To stop servers, you should use:

docker-compose down

IMPORTANT: The MySQL and Redis data are persisted. The kafka topics doesn't. You can change the docker-compose to persist Kafka data too

MySQL Schema creation

After start servers, you need to create the schemas needed by the services.

To do that, you should connect in mysql using root/admin12345 credentials and execute the following commands:

create schema academic;
create schema avalia;
create schema gaia;

Execute Services

To execute services, you should have Java 11 and execute the following command in each project root folder:

gradle bootRun

You can access a Swagger interface to test CRUD in Academic service endpoint at the following URL:

Academic Service: http://localhost:8081/swagger-ui.html

What you can check

When you create, update or delete entities, a message is published in kafka with the operation using the following payload (sample):

{
  "type": "CREATE",
  "entity": "Professor",
  "payload": "{\"id\":\"12314\",\"name\":\"Professor 1\"}"
}

The message has the operation type (CREATE/UPDATE/DELETE), the entity type and the entity payload.

We have specific topics for each entity, to test event-carried way. For the message above, we publish a message in TABLE_PROFESSOR topic, using the id as a key and the followin payload as message body:

{
  "id": "12314", 
  "name": "Professor 1"
}

The academic-service listen the first topic and the gaia-service listen each TABLE topic. They should update its local services databases with the operations.

To learn more